Reflex klystron electrondischarge device



Feb. 26,, E952 g. c. GARDNER fi mm REFLEX KLYSTRON ELECTRON-DISCHARGEDEVICE Filed Sept. 15, 1946 l/V WW 70/ 2. mam/Q0 c GARD/Vf/Q PatentedFeb. 26, 1952 REFLEX KLYSTRON ELECTRON- DISCHARGE DEVICE Bernard 0.Gardner, Waltham, Mass., assi nor to Raythecn Manufacturing Company,Newton, Mass, a corporation of Delaware Application September 13, 1946,Serial No. 696,796

8 Claims.

This invention relates to electron-discharge devices, and moreparticularly to electron-discharge devices of the velocity-modulatedtypes known as klystrons and reflex klystrons.

In certain instances, cavity resonators'with which tubes of thischaracter are commonly associated, are variable in Volume in order tovary the frequency, and therefore also the wavelength, of the output ofsuch tubes over a small range, for example, over a range of the order ofone centimeter in wavelength. Generally, for economy in production, itis desirable to produce cavity resonators of uniform size and tubes ofuniform dimensions and configuration, while at the same time it isdesirable to be able to shift the output frequency of said tube intodifferent frequency ranges or bands.

It is, there ore, an object of this invention to devise means forreadily shifting the output frequency band of an electron-dischargedevice of the klystron or reflex klystron type.

Another object is to provide a novel means for continuously varying thetuning of a reflex klystron.

A further object is to provide a plurality of different means, adaptedto be interchangeably applied during the life of the klystron, forshifting the klystron output frequency into a plurality of differentbands.

A still further object'is to devise means whereby, with a given klystronand with a given cavity resonator, the output frequency of said klystronmay be easily shifted into a different band.

These, and other objects of the present invention, which will becomemore apparent as the detailed description thereof progresses, areattained, briefly, in the following manner:

- An evacuated, dielectric envelope is provided to enclose an electrongun, a pair of grids spaced from said gun, and a repeller electrodespaced from said grids. Said grids are sealed through the walls of saidenvelope and are connected,

respectively, to the terminals of a tuned circuit. Said tuned circuitconsists of a cavity resonator which is external of the said envelope. Ametallic conducting member or band is adapted to be placed, externallyof said envelope, between said grids, but not shcrt-circuiting the same,to increase the capacitance between said grids, thereby to lower thefrequency or increase the wavelength of the'klystron output.

In the accompanying specification there is described, and in the annexeddrawing shown, some illustrative embodiments of the electrondischargedevice of the presentinventicn. It is,

ent invention is not to be limited to the details herein shown anddescribed for purposes ;.of illustration, only inasmuch as changestherein may be made without'the exercise of invention,

and within the true spirit and scope of theclairns hereto appended.

In said drawing, Fig. 1 is a longitudinal crosssection through anultra-high-frequency velocity-modulated tube embodying the invention;

Fig. 2 is a portion of Fig. 1, on an enlarge scale; s

Fig. 3 is a transverse cross-section of a modification of Fig. 1, takenon a horizontal plane substantially through the center of the cavityresonator; and

Fig. 4 is an enlarged view,.simi1ar to Fig.2 but showing anothermodification.

Referring now more in detail to one of the aforesaid illustrativeembodiments of the present invention, with particular reference to Figs.1 and 2 illustrating the same, the numeral I generally designates avelocity-modulated electrondischarge device of the type known as areflex klystron.

Said device I includes a base 2 supporting an evacuated glass envelope3. The envelope 3 may be provided with a reentrant press (not shown)supporting a highly electron-emissive cathode 4 adapted to be heated toa temperature suitable to bring about copious emission by a filament 5.Said cathode may be surrounded by a hollow accelerating electrode 6.

The electron gun structure described above produces a compact beam ofelectrons which emerges through the end of electrode 5 with therequisite velocity. This electron beam is 'subjected to the action of apair of control grid structures '1' and 8. The structure of the lowercontrol grid 7 is formed by a lead-in ring or external portion 9 whichis sealed through the side walls of the envelope 3. The internal edgesof the ring 9 are turned upwardly and form a relatively elongatedcylindrical member 18 which has an opening at its upper end across whicha perforated conducting member [9 is supported. The perforated member I9is made of fine conducting wires so as to interpose a minimum of gridsurface for intercepting the electrons contained in the electron beam.'The second (upper) control grid structure 8 is formed of a conductingring or external portion 19 sealed through the side walls of theenvelope 3. The inner ends of the ring are turned downwardly so as.to'form a relatively short cylindrical member 20 having'an opening atthe lower end thereof across which is supported a perforated member 2|likewise formed of fine conducting wires.

Spaced from said grids "I and 8 is a repeller electrode H which may besup-ported, for exam ple, at the end of a lead-in conductor l2 sealedthrough the envelope 3 at the end thereof opposite the base 2.

A hollow resonant chamber member l3, which may conveniently be atoroidal cavity resonator open along its inner edge, mates at its upperand lower edges respectively with portions l and 9 of the gridstructures. lf'he resonant chamber member 13 is preferably formed of ahighly conductive material, such as copper. Said cavity resonator may beconsidered or termed a tuned or resonant circuit. The oscillations whichare produced by the device may be picked up by a coupling loop 14,placed within the chamber member l3, and led oil by a conductor whichconveniently may be surrounded by a pipe l6 fastened into the chamber l3so as to form a concentric or coaxial line with the conductor lb.

The chamber or cavity resonator 13 may have its edges permanentlysecured to the external portions 9 and 10 of the grids i and 8 ifdesired, but said chamber-is preferably adapted to be re movablyattached to said external portions of the grids in a manner well knownto those skilled in the art to which this invention relates. The cavityresonator I3 is adapted to be tuned in any well known manner, forexample as disclosed in my copending application, Ser. No. 625,732,filed October 31, 1945, now Patent No. 2,488,906, issued Nov. 22, 1949.

The envelope 3 is formed of a plurality of sections 3a, 3b, and 3c, thesection 3a extending from lead-in conductor 12 at the top of the deviceto external portion ll] of upper grid structure 8, the section 3bextending between grid structures 8 and I, and the section 30 extendingbetween external portion 9 of lower grid structure 1 and the base 2.Section 3b is preferably of outwardly concave shape as shown.

Mounted on the external surface of said sec tion 31) is a capacity bandH made of a highconductivity metal. Band I? extends entirely aroundsection 319 between the external portions 9 and ID of grid structures 1and 8 and may touch neither of said external portions or either one, butnot both, of said external portions; in the drawing it is shown astouching neither. Band I! may be a removable clamp band or a coating,for example, although it is shown in the drawing as a metallic coating;if the clamp-band con tains an iron alloy for purposes of strength, itshould be plated with a high-conductivity (lowresistivity) metal.

In a parallelplate condenser, such as that provided between the externalportions 9 and III of the grid structures, it is well known that thecapacitance thereof has a certain value depending upon, among otherthings, the distance be tween the plates. If a conducting band is addedbetween the parallel plates 9 and it), the effect is to place a pair ofcapacitances (those between the band i! and the respective plates 9 andIll) in parallel with the inherent capacitance between plates 9 and I0,and since parallel capacitances are added to get the resultant capacitance, the resultant capacitance of the parallel-plate condenser isincreased. If band I! touches one of the parallel plates 9 or Iii, theresultant capacitance of the parallel-plate condenser may be looked uponas being increased due to the decrease in distance between the plates,since the capacitance of a parallel-plate condenser is inverselyproportional to the distance between the plates.

As will be seen from the drawing, the capacitance between externalportions 9 and I5 of the grid structures is effectively in parallel withthat between grid members i9 and 2| themselves, so that, if thecapacitance between the external portions 9 and I0 is increased, thetotal or overall capacitance of the resonant circuit provided by theinductance and capacitance of the cavity resonator I3 is increased.Since the frequency of oscillation of a klystron is inverselyproportional to the capacitance of the resonant circuit thereof,addition of capacitance by the band ll will decrease the frequency, orincrease the wavelength of the oscillations thereof with a given outercavity. Thus, by the addition of the capacity band, the range offrequencies, over which the klystron may be tuned, by variation in thevolume of the cavity resonator, may be shifted to a lower frequency bandin the electromagnetic spectrum.

Also, since ordinarily the cavity must be enlarged to lower thefrequency, and since with this invention the frequency may be loweredwithout enlarging the cavity, this invention permits the use of asmaller cavity for a given frequency.

If a removable clamp band is utilized for capacity band [1, as suggestedabove, it is possible to provide removable clamp bands of differentwidths, whereby different capacity changes, and thereby also differentbands of frequencies, may be readily obtained by selectively using eachof the plurality of clamp bands with the some klystron and with the samecavity resonator.

When the tube I is energized with the proper potentials, a beam ofelectrons coming from the cathode 4 will be accelerated by theaccelerating electrode 6, and pass through the grid structures 1 and 8.As the beam emerges from the grid structure 8, it is reflected by therepeller electrode 1 I back through the pair of control grids 1 and 8.As is well known, the initial passage of the beam through the controlgrids I and 8 produces a bunching action, and upon reflection andrepassage of the beam through these control electrodes, a debunchingaction results which feeds ultra-high frequency energy to the resonantcircuit formed by the hollow resonant chamber 13, thus setting-upultra-high-frequency oscillations which may be led off from the coaxialline I5, l6.

Now referring to Fig. 3, which represents a modification, a means forcontinuously varying the tuning of a reflex klystron is shown. In thisfigure, parts which are the same as those of Fig. 1 are denoted by thesame reference numerals. This figure is a transverse cross-section of areflex klystron, taken on a horizontal plane substantially through thecenter of the cavity resonator, and looking downwardly. Extendingthrough an aperture 22 in the side wall of cavity resonator l3, into theinterior thereof, is one end of a coiled spring-like metallic member 23.Member 23 is a relatively fiat coiled spring-like member similar tothose often found in clocks, and is of sufficient length, and isadapted, to extend from the exterior of cavity resonator l3,transversely through said resonator,. to and entirely around theexterior of section 3b of the envelope. This member is of such heightthat it will pass between the external portions of the two gridstructures without contacting simultaneously both of said portions;said-member is made ofa low-resistivity material or is plated with sucha material. The portion of member 23 which is outside the cavityresonator l3 at any particular timeis coiled up in, and enclosed by, asuitable casing 24 which is mounted on the outside of cavity resonatorI3 adjacent aperture 22. Member 23' is adapted to be fed, in acontinuous and reversiblemanner, by any suitable means (not shown), fromcasing 24, through slot 22 and cavity resonator l3, to and aroundsection 3b of the envelope, between the external portions of the gridstructures. Member 23, because of its inherent curvature, tends tofollow closely the exterior surface of section 31) of the envelope, whenit is fed toward said exterior surface.

The member 23 acts as a capacity band to vary the tuning of the klystronin the same manner as band I! of Fig. 1, except that the capacityvariationcaused by member 23 is continuous, between limits, due to thestructure of said member. Due

' the klystron is continuously variable, because of the continuousnature of the selective movement of member 23 between the parallelmlatesof the grid structures.

Of course, as member 23 is removed from between the plates 9 and I0, thecapacitance of the condenser is decreased, thereby increasing thefrequency to which the klystron is tuned.

Referring now to Fig. 4, which is an enlarged partial view of anothermodification, the sections of envelope 3 are shown at 3a, 3b, and 30. Athin metallic plate 25, of relatively limited area, is secured toexternal portion or ring 9 of grid structure 1 and extends, adjacent theexterior surface of section 31) of the envelope, toward external portionII! of the grid structure 8, but falls short thereof. A spring member25, made, as is plate 25, of a metal of low resistivity, and having anarea comparable to that of plate 25, is secured to external portion Iiiof the grid structure 8, extending toward ring 9 in such a position thatit overlies, but is spaced from, plate 25. Spring member 25 has a freeend which overlies plate 25 and is adapted to be moved with respectthereto.

In order to control the relative position of members 25 and 26 in acontinuous and reversible manner from the exterior of the cavityresonator I3, I provide an elongated small-diameter shank 21, one end ofwhich bears against the outer surface of Spring member 26, said shankpassing freely through an aperture in the outer wall of said resonatorand the other end of said shank being fastened securely to a stud 28exteriorly or said resonator. Said stud is in threaded engagement with abushing 29 mounted on the exterior surface of said resonator and isadapted to be manually rotated to positively move member 26 towardmember 25, or to allow member 25 to move away from member 25 due to itsresiliency.

Since members 25 and 2% are both conducting and since member 25 isattached to ring 9 and member 26 to ring ill, it is apparent that, whenmembers 26 and 25 are moved closer to each other, the effective distancebetween rings 9 and Ill is reduced, so that the capacitance of parallel-It is plate condenser 9-40 is increased; when members 26 and 25 aremoved further apart, the capacitance of said condenser is decreased.When the capacitance of the parallel-plate condenser 9IU is increased,as in Fig. 1, the frequency to which the klystron is tuned is lowered ordecreased. When the capacitance of condenser 9-! is decreased, thefrequency to which the klystron is tuned is raised or increased. Sincethe spacing between members 25 and 26 may be continuously varied,between limits, in either direction, it is obvious that means forcontinuously varying the tuning of the klystron has been devised orprovided.

If desired, a plurality of springs and cooperating metal bands, such as25 and 26, may be provided around the circumference of section 32), withthe plurality of spring members being arranged to be moved by a commonoperating means. Adjacent metal bands should be spaced from each other,although this is not essential.

Of course, it is to be understood that this invention is not limited tothe particular details as described above, as many equivalents willsuggest themselves to those skilled in the art. It is accordinglydesired that the appended claims be given a broad interpretationcommensurate with the scope of this invention within the art.

What is claimed is:

1. In an electron-discharge device: a dielectric envelope; an electrongun, a pair of grids, and a repeller electrode enclosed in saidenvelope; said grids being sealed through the walls of said envelope andhaving 'an inherent capacitance therebetween; a resonant circuit theterminals of which are connected, respectively, to said grids; saidresonant circuit including said capacitance; and a metallic memberexternally mounted on said envelope between the lead-in portions of saidgrids, for modifying the value of said capacitance.

2. In an electron-discharge device: a dielectric envelope; an electrongun, a pair of grids, and a repeller electrode enclosed in saidenvelope; said grids being sealed through the walls of said envelope andhaving an inherent capacitance therebetween; a cavity resonator theterminals of which are connected, respectively, to said grids; saidcavity resonator including said capacitance; and a metallic memberattached directly to the external surface of said envelope between thelead-in portions of said grids, for modifying the value of saidcapacitance.

3. In an electron-discharge device 5 a dielectric envelope; a pluralityof electrodes enclosed in said envelope; at least two of said electrodesbeing sealed through the walls of said envelope and having an inherentcapacitance therebetween; and a metallic band externally mounted on andtightly encircling said envelope between the leadin portions of said twoelectrodes, for modifying the value of said capacitance.

4. In an electron-discharge device: a dielectric envelope; a pluralityof electrodes enclosed in said envelope; at least two of said electrodesbeing sealed through the walls of said envelope and having an inherentcapacitance therebetween; a resonant circuit the terminals of which areconnected, respectively, to said two electrodes; said resonant circuitincluding said capacitance; and a metallic band externally mounted onand tightly encircling said envelope between the leadin portions of saidtwo electrodes, for modifying th value of said capacitance.

5. In an electron-discharge device: a dielectric envelope; an electrongun, a pair of grids.

and a repeller electrode enclosed in said envelope; said grids beingsealed through the walls of said envelope and having an inherentcapacitance therebetween; a cavity resonator the terminals of which areconnected, respectively, to said grids; said cavity resonator includingsaid capacitance; and a metallic band externally mounted on and closelyencircling said envelope between the leadin portion of said grids, formodifying the value of said capacitance.

6. In an electron-discharge device: a dielectric envelope; a pluralityof electrodes enclosed in said envelope; at least two of said electrodesbeing sealed through the Walls of said envelope and having an inherentcapacitance therebetween; a pair of overlying but radially-spacedmetallic plate members external of said envelope and between the lead-inportions of said two electrodes; each one of said pair of members beingattached to a different one of said two electrodes and the outer one ofsaid pair of members being resilient; and means operable to vary thespacing between said members to thereby modify the value of saidcapacitance.

7. In an electron-discharge device: a dielectric envelope; a pluralityof electrodes enclosed in said envelope; at least two of said electrodesbeing sealed through the walls of said envelope and having an inherentcapacitance therebetween; a resonant circuit the terminals of which areconnected, respectively, to said two electrodes; said resonant circuitincluding said capacitance; a pair of overlying but radially-spacedmetallic plate members external of said envelope and between the lead-inportions of said two electrodes; each one of said pair of members beingattached to a difierent one of said two electrodes and the outer one ofsaid pair of members being resilient;

and means operable to vary the spacing between said members to therebymodify the value of said capacitance.

8. In an electron-discharge device: a dielectric envelope; an electrongun, a pair of grids, and a repeller electrode enclosed in saidenvelope; said grids bein sealed through the walls of said envelope andhaving an inherent capacitance therebetween; a cavity resonator theterminals of which are connected, respectively, to said grids; saidcavity resonator including said capacitance; a pair of overlying butradially-spaced metallic plate members external of said envelope butwithin said cavity resonator and between the lead-in portions of saidgrids; each one of said pair of members being attached to a differentone of said grids and the outer one of said pair of members beingresilient; and means operable externally of said cavity resonator tovary the spacing between said members to thereby modify the value ofsaid capacitance,

BERNARD C. GARDNER.

REFERENCES CITED The following references are of record in'the file ofthis patent:

UNITED STATES PATENTS

